The present invention is directed to a method and apparatus for attaching a cranial flap to a skull, from which the cranial flap was removed, during surgery.
Surgical operations involving the human skull, such as brain surgery or craniofacial surgery, require that a section of the skull be removed. Typically, a number of burr holes are first drilled into the skull and which outline the section of the skull to be removed. A cutting tool is then inserted into one of the burr holes and a cut, or osteotomy, is made from one burr hole to then next burr hole until a loop is completed. The loop of osteotomies forms an opening in the skull and defines the section of the skull to be removed. The section of the skull to be removed is commonly referred to as a cranial flap. Because the blade on the cutting tool typically has a width of 1-2 mm, a kerf is formed between the opening in the skull and the cranial flap. Thus, the periphery of the cranial flap is smaller than the opening in the skull.
When the surgical procedure inside the skull is complete, the cranial flap must be replaced in the opening in the skull and re-attached to the skull. A number of methods are known for re-attaching the cranial flap to the skull. One known method uses stainless steel wire as a suture material. Other known methods utilize plates and associated screws made from either titanium or a bioabsorbable polymer. Still other known methods employ rivet-type fasteners made of titanium or a biocompatible polymer such as acetyl resin.
A major disadvantage of the known methods for reattaching a cranial flap that use a metallic material is that the metal creates large artifacts in any subsequent CT scans and radiographs. It is also disadvantageous to use a permanent (non-bioabsorbable) fastener that protrudes more than 1-2 mm from the surface of the skull because the fasteners then become visible as unsightly bumps under the patient""s skin.
The present invention is an apparatus for attaching a cranial flap to a skull during surgery. The cranial flap and the skull are spaced apart by a kerf defined by a first kerf edge on the cranial flap and a second kerf edge on the skull. The apparatus comprises at least one attachment device made of a bioabsorbable polymeric material. The at least one attachment device has a head portion, a main body portion, and an end portion that is deformable upon heating to a predetermined temperature. The end portion of the at least one attachment device has a first condition in which the end portion extends axially from the main body portion and a second condition in which the end portion extends radially from the main body portion and engages an inner surface of the cranial flap. The end portion is deformable from the first condition to the second condition during surgery by heating the end portion and forming the end portion around the first kerf edge of the cranial flap to clamp the at least one attachment device to the cranial flap. The main body portion of the at least one attachment device includes a first surface portion that attaches to the first kerf edge on the cranial flap and a second surface portion that attaches to the second kerf edge on the skull. The at least one attachment device is positionable in the kerf between the cranial flap and the skull to secure the cranial flap to the skull by frictional engagement between the first surface portion against the first kerf edge and frictional engagement between the second surface portion against the second kerf edge.
The present invention also provides a method for re-attaching a cranial flap to a skull during surgery. The method utilizes an attachment device made of a bioabsorbable material that is formable upon heating to a predetermined temperature. The attachment device has a head portion, a main body portion, and a deformable end portion extending axially from the main body portion. The attachment device is placed adjacent the cranial flap so that the head portion engages an outer surface of the cranial flap and the main body portion engages a first kerf edge of the cranial flap. The end portion of the attachment device is heated to a predetermined temperature and subsequently bent around the cranial flap so that the end portion extends radially and engages an inner surface of the cranial flap. The cranial flap is then pressed into an opening in the skull created by the removal of the cranial flap so that frictional engagement between the main body portion of the attachment device and the cranial flap and frictional engagement between the main body portion of the attachment device secures the cranial flap to the skull.